Aetiology

For the upper limb to be clefted, embryogenesis must be affected between days 39 to 50 of embryogenesis. Classically, it was thought that there was a wedge-shaped defect of apical ectoderm within the limb bud that misdirected the formation of proximal structures. However, it has been suggested that there is a difference in aetiology between typical and atypical cleft hands. Typical cleft hands may result from fusion of digital rays bordering the defect, with or without polydactyly, rather than a deficiency of central constituents. Atypical cleft hand is more likely to be due to apoptosis of central hand elements with incomplete regeneration.

Most cases of cleft hand are sporadic gene mutations but clefting is associated with a number of syndromes. Specifically, an area on chromosome 3q27 seems to be mutated in the condition split-hand and split foot (SHSF). This region codes for genes that have a role in the maintenance of the apical ectodermal ridge.